Seal Design Research Articles

Quantifying the heat transfer effect of the axial turbine stator well cavity

A Thermal-Fluid-Structural model is presented for quantifying the heat generation by the labyrinth seal in the low-pressure turbine stator well cavity. The method combines windage heating and convective heat transfer effects for labyrinth seal design, making it possible to use the heat transfer boundary condition instead of adiabatic to do the computational fluid dynamic calculation. The solutions illustrate how the outlet total temperature may change depending on the seal pressure ratios, windage heating, and heat transfer coefficient. It is further demonstrated that with a fixed seal pressure ratio, the thermal boundary condition has little influence on the leakage flow rate of the seal. The total temperature rise is dependent on the thermal boundary conditions, including the stator/rotor wall temperature, heat transfer coefficient, and windage heat caused by air friction.

Optimization of Basket Oven Oil Seal Design For Quality, Productivity and Material Handling

In the oil seal production process, one of them is the post-cure oven process as a heat treatment to engineer the rubber material so that it has resistance to friction and has high heat resistance. The post-cure oven process itself uses equipment in the form of an oven basket made of heat-resistant steel material to place the oil seal. However, the Basket oven itself has a maximum limit for placing the oil seal in the oven, so calculations are needed to find the optimization value to find out the maximum value obtained so as to increase work productivity. From the problems found, the existing oven baskets were unable to accommodate 1,442 pcs/lot of products, but were only able to accommodate 1,344 pcs of products. so it is necessary to design a new basket oven to get the optimal value so that the basket oven can accommodate as many as 1,442 pcs/lot of products. From the research results it is known that to save material the most optimum cutting value is if the value of x = 8.5. Meanwhile, to get the maximum volume value, it is cut with a value of x = 11. By using the new oven basket, the product volume that can be accommodated is 1,568 pcs when compared to the use of the old basket which was previously able to accommodate 1,344 pcs of product. The use of a new basket oven can increase basket volume by 16.7%.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ РАСХОДНЫХ ХАРАКТЕРИСТИК ЯЧЕИСТО-ЛУНКОВОГО УПЛОТНЕНИЯ ДЛЯ ПАРОВЫХ ТУРБИН

In this paper, a study of the flow characteristics of a seal with a cellular stator is carried out. The rotor had a well surface with a diameter of d = 10 mm and a depth of h = 1 mm. The stator part is made of stamped rings and radial plates, forming a cellular structure with a rectangular cross section. Holes were made on the outer plate to separate moisture into the sealing chamber behind the stator. A series of experiments were carried out with a fixed disk and rotating at different speeds (1000; 2000; 3000 rpm). The results of the construction of consumption characteristics showed that the effect of rotation is negligible. Numerical research at Ansys revealed the complex spatial nature of the gas flow in the flow part of the seal with the formation of reverse vortex flows. In a seal with wells, the vortices in the cells, on the contrary, have a more gentle structure. The strengthening of vortex structures is associated with a changing gradient of the area of the wells, where local acceleration of the main flow occurs, which, in turn, pumps the perturbed flow into the cells. The numerical calculation and field experiment performed have shown the effectiveness of using this seal design for steam turbines, especially in nodes of large axial displacements of the shaft line relative to the housing.

Rotordynamic characteristics of a novel labyrinth seal with partition walls and helical groove teeth

To improve the stability of the conventional labyrinth seal (LS), in this paper, four novel fully partitioned helically labyrinth seals (FPHGLS) were designed and they were in comparison with one FPPGLS. The influences of the preswirl ratio and the helical groove pitch on the leakage flow and rotordynamic characteristics were numerically investigated, using the transient computational fluid dynamics (CFD) method based on the multi-frequency elliptical whirling orbit model. The accuracy and availability of the present transient numerical method were demonstrated based on the experiment data. The results show that the partition walls design can significantly increase the direct damping and cross-coupling stiffness for labyrinth seals and the helical teeth design can significantly decrease the cross-coupling stiffness and tangential force. When the helical groove pitch is equal to the seal length, the leakage nearly remains unchanged. Compared to the baseline design (LS), the FPPGLS and the FPHGLS have similar and significantly larger direct stiffness and direct damping. The two designs possess positive direct stiffness throughout the frequency range. The FPPGLS and FPHGLS possess significantly higher direct damping (∼323.7% larger than LS). But the FPPGLS possesses the largest cross-coupling stiffness among three seals at two preswirl ratios. From preswirl ratio = 0.13–0.84, the cross-coupling stiffness of the FPHGLS decreases by 53.4-310.1% compared with the FPPGLS. Increasing the helical groove pitch increases both direct stiffness and direct damping and reduces cross-coupling stiffness, but it also leads to greater leakage losses. In general, the novel FPHGLS whose helical groove pitch is equal to seal length possesses superior rotordynamic characteristics and similar leakage characteristic. This work provides the reference of the seal design and safety operation for the turbomachinery.

Dynamic Characterization of an Adaptive Film-Riding Seal

Abstract Shaft seals control the leakage of fluid between areas of high pressure and low pressure around rotating components inside turbomachinery. Static seals are often subject to damaging rubs with the shaft, caused by assembly misalignments and rotordynamic vibrations during operation. Adaptive seals aim to reduce leakage flows whilst minimizing wear. The film riding pressure actuated leaf seal (FRPALS) is one such design which utilizes a large installation clearance and is blown down toward the shaft under pressure. This paper presents a numerical model which can be used in the design and development of adaptive shaft seals, validated by experimental data from the literature. The model uses a modified version of the Reynolds equation to predict the dynamic, frequency-dependent stiffness and damping coefficients of the fluid film. The dynamic coefficients have been solved for different operational clearances and pressure differences to generate coefficient maps. These maps have been incorporated into a blow down model with compliant mechanical leaves to predict the transient translational and angular displacement paths of the FRPALS when subject to an increasing pressure drop. The blow down model has been compared against experimental measurements collected from a specially designed test facility for the characterization of shaft seal performance. Eddy current probes were used to measure the displacement paths of the FRPALS with the experimental values showing that the model can accurately predict the dynamic movement of the seal when subject to a pressure difference.

High-Temperature Flow Behavior and Energy Consumption of Supercritical CO2 Sealing Film Influenced by Different Surface Grooves.

The Brayton cycle system, as a closed cycle working under high-temperature, high-pressure and high-speed conditions, presents significant prospects in many fields. However, the flow behavior and energy efficiency of supercritical CO2 is severely influenced by the structures of face seals and the sealing temperature, especially when the sealing gas experiment is the supercritical transformation process. Therefore, a numerical model was established to investigate the high-temperature flow behavior and energy consumption of face seals with different surface grooves. The effects of the operation parameters and groove structure on the temperature distribution and sealing performance are further studied. The obtained results show that the supercritical effect of the gas film has a more obvious influence on the flow velocity uθ than ur. Moreover, it can be found that the temperature distribution, heat dissipation and leakage rate of the gas face seals present a dramatic change when the working condition exceeds the supercritical point. For the spiral groove, the change rate of heat dissipation becomes larger, from 3.6% to 8.1%, with the increase in sealing pressure from 15 to 50 MPa, when the temperature grows from 300 to 320 K. Meanwhile, the open force maintains a stable state with the increasing temperature and pressure even at the supercritical point. The proposed model could provide a theoretical basis for seal design with different grooves on the supercritical change range in the future.

Design and analysis of combined standard ferrofluid and centrifugal seals

PurposeFerrofluid seals are known for their low friction torque and high tightness. However, they have some limitation due to the allowable rotational speed. The work presented here analyzes the performance of newly designed seals which are a combination of a ferrofluid and a centrifugal seal. The new seals can operate at high speeds. The purpose of this study is to theoretically predict the performance of combined seals.Design/methodology/approachThree seals were designed and selected for analysis. A version of the seals with a nonmagnetic insert is also considered, the purpose of which is to facilitate the installation and return of ferrofluid during low rotational speeds. The analyses were based on combining the results of numerical simulation of magnetic field distribution with mathematical models.FindingsA combination of ferrofluid sealing and centrifugal sealing is possible. Analyses showed that the combined seal could hold a minimum pressure of 190 kPa in the velocity range of 0–100 m/s. The problem with this type of seal is the temperature.Originality/valueNew seal designs are presented. Key parameters that affect the seal operation are discussed. A methodology that can be used in the design of such seals is presented.Peer reviewThe peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2023-0221/.

Evolution and Action Mechanism of Relative Negative Pressure Zone in Spiral Groove Gas Face Seal for Aero-Engine

Abstract As an advanced sealing technology, the application of gas face seal in aero-engine is few; if possible, lower specific fuel consumption, higher thrust-weight ratio, and effective secondary flow control at minimal cost would be brought. A relative negative pressure zone (RNPZ) was found in the spiral groove gas face seal, and the evolution and action mechanism of RNPZ was investigated in detail, which may promote the above application. Three film thicknesses of spiral groove gas face seals at different rotational speeds and inlet pressures were numerically compared to obtain the pressure field in the groove area and the formation of RNPZ. Then, the radial and circumferential velocities in the groove were calculated to quantify the impact of the obstruction effect, viscous pumping, and shear effect, which revealed the evolution mechanism of the RNPZ stage by stage. At last, the action mechanism of RNPZ was clarified through the hydrodynamic performance analysis. It is found that the pressure field evolution in the gas face seal is in stage Ⅲ under the high rotational speed and low inlet pressure conditions in an aero-engine. Under the same film thickness, RNPZ can suppress leakage to a certain extent in stage Ⅱ, while in stage Ⅲ, it increases the opening force and stiffness-leakage ratio. This work can provide theory and data to help with the subsequent optimization design of gas face seals for aero-engine.

Comparing Solar Heater Designs: Evacuated Tube Vs. Flat-Plate Collectors

In terms of solar heater designs, this study compares the characteristics of collectors made from evacuated tubes (ETCs) as well as collectors with flat plates (FPCs). Due to their reduced heat loss, ETCs—which have individual tubes made of glass with a sealed under-vacuum double-wall design—perform exceptionally well in colder climates. FPCs, in comparison, are more affordable but less effective since they include a simpler absorbent plate that fits inside of a flat panel. These designs can be implemented using the SolidWorks software, which permits precise 3D modeling as well as simulations. According to research, ETCs are appropriate for colder locations since their vacuum insulation reduces heat loss along maintains greater temperatures. Even while radiation losses make FPCs less efficient, they are still excellent at collecting daylight energy, specifically in warmer climates. Decision-makers looking for sustainable cooling solutions might benefit from analysis that takes into account technical characteristics, financial viability, and geographical compatibility.

Experimental study of self-locking seal structure based on full ocean depth sediment pressure retaining sampler

The full ocean depth environment is characterized by high pressure, low temperature, and high corrosiveness, making it difficult for the current deep-sea sampling equipment to obtain pressure-retaining sediment samples from the seafloor. A new self-locking seal structure is designed with an automatic centering plus floating valve core structure to ensure that the long needle valve core only carries the axial load and autonomously fits the sealing cone of the pressure retaining device. The novel self-locking seal design makes the sampler seal more reliable under high pressure. We conducted a series of experiments to verify the sealing performance of the self-locking seal structure, and the test results show that the self-locking seal structure has better sealing performance when the pressure difference between the inside and outside is larger. This new self-locking seal structure has been used for the full ocean depth sediment sampler during the TS-21 cruise in 2021 and was tested in situ at a depth of 7700 m in the West Philippine Basin, retrieving pressure-retaining sediment samples with 94 % pressure retention.

Adhesion Performance of Rubber Modified Asphalt in Chip Seal: A Molecular Dynamic Study.

Chip seals are widely used for asphalt pavement maintenance, yet the understanding of the interaction between asphalt and aggregates embedded in the asphalt layer remains limited. This paper aims to quantify the interaction between asphalt and aggregate at the microscope level to better understand their adhesion performance in chip seals. Rubber-modified and neat asphalt models are established and verified based on various parameters, including density, viscosity, solubility, glass-transition temperature (Tg), and cohesive energy density (CED). Subsequently, nanoindentation simulation is employed to analyze the adhesion force and interface stress between aggregates and asphalt, considering different embedded depths and pull-off speeds. The adhesion energy between asphalt and silica is also calculated. The results indicate that rubber-modified asphalt exhibits lower density, CED, solubility parameters, and Tg while having higher viscosity than neat asphalt. The adhesion force and interface stress display a quadratic relationship with embedded depths and pull-off speeds. Furthermore, the bond between rubber-modified asphalt and silica is stronger than that between neat asphalt and silica. These findings advance the comprehension of asphalt-aggregate adhesion in chip seals and offer insights for optimizing chip seal design through molecular simulation, thereby potentially enhancing asphalt pavement performance.

Characterizing Shrouded Stator Cavity Flow on the Performance of a Single-Stage Axial Transonic Compressor

Abstract Shrouded stator cavity flow increases the stator total pressure loss, reduces the compressor isentropic efficiency, and thus limits the compressor pressure rise capability. This paper proposes a simplified cavity flow model that consists of flow injection at the stator inlet and flow suction at the stator outlet. Based on this model, a full-factorial parametric study on the leakage flow ratio and the leakage swirl angle is performed at different rotational speeds and incidences. In the first place, the effectiveness of the numerical method is validated against the experimental data based on the full-scale cavity geometry; then, the numerical simulations on the simplified cavity geometry are validated against that of the full-scale one. Results show that the leakage flow ratio plays a dominant role in determining the compressor performance penalty. The isentropic efficiency drops almost linearly with the leakage flow ratio due to deteriorated near-hub separations, and the slope becomes steeper at higher operating speeds and incidences. The leakage swirl angle only has a pronounced effect under a high leakage flow ratio. The efficiency penalty reduces with increasing swirl angle due to an alleviated tangential flow mixing and suppressed near-hub separations. The swirl angle effect is more pronounced at lower incidence conditions. These findings advance the fundamental understanding of shrouded stator cavity flow effects and provide useful guidance for cavity seal designs.

Optimization method of high parameter spiral groove mechanical seal based on axiomatic design theory

At present, in order to improve the performance of spiral groove mechanical seals, the structural parameters of seals are mostly adjusted based on the experience of designers. The integration degree of existing mechanical seal performance research examples is low, and the whole performance optimization process lacks of scientific theoretical framework to guide. In order to solve this problem, combining the axiomatic design theory with the existing mechanical seal performance research, a structural optimization method of spiral groove mechanical seal based on axiomatic design theory was put forward. This method defines the mapping relationship between the three-level functional requirement domain and the design parameter domain of the spiral groove mechanical seal, and thus develops 14×14 diagonal optimization matrix. The research results show that the introduction of axiomatic design provides a basic theoretical framework for the performance optimization of spiral groove mechanical seals and decomposes the optimization process into several design modules, which improves the efficiency and accuracy of the optimization design of spiral groove mechanical seals and has good application value.

Study on the effect of bubble number on the collapse of a multi-bubble system near the rigid wall

The mechanism of multi-bubble collapse is one of the key technologies that need to be overcome in the development of large submersibles, which is urgently needed to study and explore. The VOF method is used to study the collapse process of a multi-bubble system near the rigid wall. The bubble collapse process is analyzed under three different bubble numbers and four different initial bubble wall distances. The influence of the number of bubbles and initial bubble wall distance on the bubble collapse process is obtained, and the mechanism of multi-bubble collapsing near the rigid wall is revealed. The results indicate that in a multi-bubble system, as the number of bubbles increases, the duration of bubble collapse increases, the minimum bubble radius decreases, and the maximum central pressure increases. The closer the bubble is to the rigid wall, the longer the duration of bubble collapse, which also lead to fluctuations in the maximum center pressure and maximum interface velocity of a multi-bubble system. The results of this study are expected to provide a theoretical basis and technical support for the design and performance optimization of deep submersible mechanical seals.

ИССЛЕДОВАНИЕ КОЭФФИЦИЕНТА ТРЕНИЯ ПОЛИМЕРНЫХ МАТЕРИАЛОВ ДЛЯ 3D-ПЕЧАТИ ЭЛЕМЕНТОВ КОНСТРУКЦИИ ПОДВИЖНОГО СОСТАВА

Additive technologies are represented by various methods of 3D printing and are increasingly being used in various industries around the world. For example, printing with metal powders is used for the production of such structural elements as various arm supports in the aircraft industry or the manufacture of spacecraft hulls. The use of 3D printing with the use of polymer materials makes it possible to manufacture, for example, various gears for non-principle mechanisms. The use of such technology in pneumatics is also relevant. However, at the same time, the possibility of using these technologies for the manufacture of various pneumatic devices has not been widely studied up to now. In the course of studying this issue, a pneumatic gearbox was made. However, it was found out that one of the problems that does not allow to design and manufacture a normally functioning pneumatic device is an unknown value of friction factor of the materials of which its elements are made.
 The study objective is to find out the static friction factor of products made of polymer materials using 3D printing technologies. The necessity of this study is explained by the problems that arose as a result of testing a high-performance pneumatic gearbox manufactured using additive technologies applying various polymer materials. The main problem of this device is the density violation of fixed detachable joints of gearbox case parts and covers. Since the medium to be used is compressed air under a pressure of 0.9 MPa, any density violation can lead to the gearbox destruction or to air losses from the braking system of a freight train due to an increase in the number of leaks in the pipeline for additional power supply to the spare reserve.
 The paper presents the results of experimental studies on finding the friction factor of various types of materials used in 3D printing. The obtained friction factors are required for the design of seals of pneumatic devices according to generally accepted methods.

Failure mechanism of magnetic fluid seal for sealing liquids

Magnetic fluid seals are contact-free rotary seals widely used to seal gas and vacuum. However, their effectiveness declines when utilized to seal liquids due to the inherent incompatibility and instability at the interface between the two liquids. The underlying mechanism for this premature failure remains incompletely comprehended, posing a significant challenge to their widespread use for sealing liquids. Here we demonstrate a novel pole structure featuring a non-magnetic shaft, which creates a closed magnetic circuit without requiring the magnetic circuit to pass through the rotating shaft. This innovative approach enables the observation of the failure processes of the seal through a hollow transparent shaft, utilizing an endoscope. The results show that the static seal failure occurrs in two stages: extrusion, infiltration, and magnetic fluid barrier rupture. In the first stage, a leakage channel opens cyclically, whereas in the second stage, the seal leaks completely once the critical pressure is surpassed. Dynamic failure arises from the intricate interplay between dissolution, extrusion, and interface instability. Upon attaining the critical speed, the flow at the interface transitions from laminar to turbulent, leading to apparent delamination fluctuations. At this point, the magnetic fluid film becomes unstable and instantly leaks from the seal upon exceeding the critical speed. This research has unveiled crucial inducing factors for seal failure that have significant implications for the design of liquid seals. The intricate and complex nature of the failure mechanism emphasizes the need for a comprehensive understanding of the interplay between the seal design, magnetic fluid properties, and operating conditions to develop efficient liquid seals with superior performance.

Dynamic characteristics of a non-Newtonian lubrication mechanical seal with herringbone grooves considering cavitation effect

This research investigated the effect of lubricant's non-Newtonian properties on dynamic characteristics of a herringbone grooved liquid film seal (HG-LFS) considering cavitation. A modified steady-state perturbation Reynolds equation of the non-Newtonian was derived. Visualized experiments were conducted to verify the accuracy of calculations. The non-Newtonian effect on stiffness, cavitation, damping coefficients, and other sealing performance of the liquid film seal at different velocity, pressure and film thickness were discussed and analyzed. The results indicate that the seal has larger stiffness and damping coefficients with the dilatant lubricant, the cavitation can be inhibited by the shearing-thinning lubricant, and the impact of non-Newtonian on the seal stability decreases with the increase of film thickness. This study would contribute to the design and theoretical research of liquid film seals.

Digitizing protocols into single reactors for the one-pot synthesis of nanomaterials

Digitizing protocols into single reactors for the one-pot synthesis of nanomaterials

Quantifying the impact of heat in support seal configuration for aero engines

AbstractLeakage, deformations, power loss, heat generation in the support seal system and other issues are typical when support seals are developed. The design of the support seal system has progressively evolved over recent decades as part of an ongoing effort to provide effective cooling for the aero engine secondary air system. In particular, oil heat management in the oil chamber has strict requirements, which limit the heat generation of the support seal system. The potential of supporting seal research with an oil system is investigated in this work. The combination of the CFD/FEA method and quantifying the heat generation entering the oil chamber allows for improvements not just to the individual buffer air seal unit, but the oil seal together. The analysis relies on the combination of quantifying heat generation entering the oil chamber to provide a mutual influence of neighbouring labyrinth seals. The mutual influence requires further analysis, considering the thermal deformation of the rotor/stator to provide further accurate geometry parameters in preliminary seal designs. The experimental test was conducted to verify the preliminary CFD-FEA loosely coupled analysis result, which reveals that in a turbine support seal system, the radius of the buffer air seal has a significant influence on the leakage flow rate and power loss of the oil seal, which should take into account the integral influence of the pressure difference of the oil seal caused by the radius change of the buffer air seal and the running clearance of the oil seal.

High pressure sealing characteristics of combined structure based on flexible graphite rings

Seal components made of flexible graphite have excellent resistance to temperature, while sealing of high pressure fluids is unsatisfactory. The sealing behavior of flexible graphite rings is characterized by the ratio of the contact pressure to the axial pressure. The FEA results show that the lateral pressure decreases roughly linearly along the direction of the sealing path, and the lateral pressure coefficient increases with increasing axial pressure. We design a combined seal structure based on flexible graphite rings, and extract the contact pressure along two sealing paths. The results imply that the self-sealing effect is more favorable when the pressure of the sealing fluid is increased. The effect of the friction coefficient on the contact pressure is not significant, except at the beginning of the sealing path. Sealing effects are tested under the coupling condition of 350°C and 50 MPa, which verify the sealing performance under high temperature and high pressure. The comparison of the test results of “ kf” (the product of lateral pressure coefficient and friction coefficient) with those of the FEA validates the rationality of the analytical approach. The comprehensive coefficient “ kf” can be easily obtained by testing, and can be used as a key parameter for seal design.